When a toolbar is resized in such a way that it is too small to show all the items it contains, an extension button will appear as the last item in the toolbar. Pressing the extension button will pop up a menu containing the items that do not currently fit in the toolbar.

The default size is determined by the application's style and is derived from the QStyle::PM_ToolBarIconSize pixel metric. It is the maximum size an icon can have. Icons of smaller size will not be scaled up.

This signal is emitted when an action in this toolbar is triggered. This happens when the action's tool button is pressed, or when the action is triggered in some other way outside the toolbar. The parameter holds the triggered action.